Drill countersinks are known in the art for holding a drill bit, including the exemplary countersink shown in FIG. 1. A countersink tool 10 includes a proximal end 12 with a shank 14 and a distal end 16 with a cutting edge 18. The shank 14 contains an annular groove 20 for connection with an automatic or “quick-release” coupling of a drill chuck or tool holder (not shown). The shank 14 is of any suitable shape for rotatably coupled engagement with a power source, using either a male or female style coupling. Although tool shanks having hex cross-section shapes are shown herein, any shape formed to inhibit rotation of the tool relative to a tool holder or power source will suffice. Likewise, the annular groove 20 formed on the tool shank 14 is not necessary for effective automatic coupling and release of the tool relative to the tool holder or power source.
The countersink tool 10 includes a longitudinal bore 22 extending from the cutting edge 18, the bore 22 being adapted for receiving a drill bit 24 therein. The countersink tool 10 includes a body 27 having an outer wall 28 with a flute 26 formed at the distal end 16, which includes the cutting edge 18. The drill bit 24 is held in place within the bore 22 by a set screw 30 which extends through the body 27 to engage the drill bit 24. Loosening the set screw 30 releases the drill bit 24 to allow an operator to adjust the length L of the bit 24 extending from the bore 22, and tightening the set screw 30 secures the drill bit 24 within the bore 22 relative to the body 27.
FIG. 2 is a cross-sectional view of holes bored in a board 31 with the prior art countersink tool 10 shown in FIG. 1. Step 2A illustrates the countersink tool 10, with drill bit 24, boring a hole 32, or counterbore, in the board 31 to an approximate depth for flush installation of a screw 34. The length L of the drill bit 24 extending from the cutting edge 18 of the bore 22 is adjustable to match the screw length. The outer diameter of the countersink, or flute 26, defines the counterbore diameter. Step 2B illustrates the hole 32 bored by the countersink tool 10 ready for screw 34 installation. Step 2C shows an installed screw 34 with a screw head 36 flush with a work surface 37 of the board 31.
Step 2D shows a hole 35 in which the operator has bored the hole too deep for flush installation of the screw 34. In some instances the bore hole 32 may be too shallow for flush installation of the screw 34. Step 2E illustrates the countersink tool 10, with drill bit 24, boring a deeper hole 38 in the board 31 for recessed or covered screw installation. Step 2F illustrates the resultant hole bored 38 by the countersink in step 2E. Step 2G shows an installed screw 34 with a plug 40 inserted in the counterbore to cover the screw 34 and create a plug surface flush with the work surface of 37 of the board 31.
The countersink tool 10 shown and described with respect to FIGS. 1 and 2 is a single-stage countersink with a single flute. Two-stage countersinks are also known in the art for forming a counterbore having two diameters. In addition, countersinks with more than one flute and/or set screws are also known in the art.
FIG. 3 is a side view of the prior art countersink tool 10 shown in FIG. 1 holding a tool bit 24, and also including an adjustable stop collar 42 attached to the body 27 of the countersink tool 10. The stop collar 42 is placed around the flute 26 or flutes of the countersink tool 10 to prevent an operator from drilling a counterbore too deep with the countersink tool 10. The stop collar 42 includes a workpiece engagement surface 43 and a set screw 44 to secure the collar in place along the length of the body 27 of the countersink tool 10. Loosening the set screw 44 releases the stop collar 42 to permit an operator to adjust its position along the length of countersink tool 10 and tightening the set screw 44 secures the collar 42 in place relative to the body 27. Thus, the depth of the counterbore is adjustable in two ways, by adjusting the length L of the drill bit 24 extending from the bore 22 with the countersink set screw 30, and by adjusting the position of the stop collar 42 along the length of the countersink tool 10 with the stop collar set screw 44 (thus fixing a counterbore depth D between the work engagement surface 43 of the stop collar 42 and the cutting edge 18 of the body 27 of the countersink tool 10, as seen in FIG. 3).
FIG. 4 is a cross-sectional view of holes bored in a board 45 by the countersink tool 10 with attached stop collar 42 shown in FIG. 3. Step 4A illustrates the countersink tool 10 fitted with the stop collar 42 boring a hole 46, or counterbore, in the board 45 to an exact depth for flush installation of a screw 34. The length L of the drill bit 24 extending from the cutting edge 18 of the bore 22 is adjustable to match the screw length, and the depth D of the counterbore is separately adjustable to match the depth of the screw head. Step 4B illustrates the hole 46 bored by the countersink tool 10 ready for screw 34 installation. Step 4C shows an installed screw 34 with a screw head flush with a work surface 48 of the board 45. Step 4D illustrates that, in comparison to the hole 35 shown in step 2D the stop collar 42 aids in boring a hole 46 with a consistent counterbore depth for flush installation of a wood screw.
Steps 4E–4G are similar to steps 2E–2G described above with respect to FIG. 2. Step 4E illustrates the countersink tool 10 (with the stop collar 42 removed) boring a deeper hole 50 in the board 45 for recessed or covered screw installation. Step 4F illustrates the resultant hole 50 bored by the countersink tool 10 in step 4E, and step 4G shows an installed screw 34 with a plug 40 inserted in the counterbore to cover the screw 34 and create a plug surface flush with the work surface 48 of the board 45.